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Hi Everyone

Last autumn [2014] I decided that I had to do something about my 150 M2 lawn which comprised of about 20% grass, 60% weeds and 20% bare ground. In addition, the lawn was very uneven.

I spayed roundup on the lawn in October and within two weeks everything looked dead. I left it until spring then tried to rake out the dead vegetation, but I was not very successful. I then sprayed everything again, and left it for three weeks. I bought several cubic metres of top soil which I spread to completely cover the dead vegetation and to level the ground. I then grass seeded using 40gms / M2.

I watered regularly, and within two weeks the ground started to turn green. It soon became evident that it was not grass that was coming through but some plant which was extremely green. With hindsight, I should have found out then what was growing and sprayed roundup again to kill it, but summer was approaching and what had grown looked nice when cut short.

As the summer progressed and after rain, it grew so very, very quickly and retained so much water that when cutting I slide all over the place. I have now found out that what I have in place of grass is purslane.

Having now researched it it would appear difficult to remove. I am proposing to spray with a high concentration of roundup this month, wait two or three weeks and spray again. The questions I have are:

After the initial spray and when everything appears to have died, should I remove all the dead plants or leave it as it should eventually rot.

If I have to remove it then it will need to rotivate the entire area as 150 M2 is too big an area to pull up the dead plants, and I really want to avoid this.

I still have a few metres of topsoil stored in the garden, and although there is no sign of the purslane in the stockpile, I assume it must be there because I can think of no other way it grew instead of the grass seed I planted.

If I can leave the dead purslane do I need to cover it with more topsoil because the ground in now nicely level and I have already expressed above my concern at spreading topsoil from my stockpile.

Many thanks in anticipation of some replies

Even if it is "dead", I would remove the remains anyway. There may still be seeds that won't be killed by weed killers. Water a few more times to make sure all the seeds have sprouted and kill them again. You may have to repeat a couple of times.
You should not need a high concentration of round up, you should always follow the label directions. Most people try to starve or cut weeds before they round them up. Instead water the weeds and get them nice and plump but not seedy. Don't water the day before you spray. Spray Round up following the directions. It takes round up a few days to work so no water for 24 hours after. You will have to repeat until all the seeds have sprouted and the plants have been killed.

Round up should break down quickly, but do not compost the remains, bag and trash. Some other weed killers or some versions of roundup may have "extended" effects so may cause problems later on down the road, you want to avoid those if you want to plant something soon.

If the plants are dead and dry they should not be that hard to pull up because they won't be as heavy and dead roots should not resist as much.

Hi Super Green Thumb

Many thanks for replying. Much appreciated.

I have made the mistake of thinking that if I pulled the weeds and put down a covering of compost or soil, it would smother what was left. In reality when you pull up weeds from the roots, it is still a form of cultivation because it does break up the soil and let weed seeds sprout. Adding topsoil, they will just take a little longer to reach the surface, but they will be very happy.

If I plan to raise the level of the soil significantly, I put down cardboard or newpaper to block the weeds from below and then put the amended soil on top and plant in that. The cardboard and newspaper block light and if you plant thickly in the soil on top, the plants should be able to get established well enough to compete better.

Purslans is not that bad, nut sedge is much worse. We rented our house for 3 years and when we got back the tennants had mowed but not watered anything and my yard had a sprinkler system. The grass and the tree with the neglect were in such poor condition that the nut sedge had invaded the grass and it was more nut sedge than grass. Because the yard was not watered the tree had a lot of dead and weak branches from being starved. I tried over a year to dig out the nut sedge and finally called a landscaper to replant the grass. He told me that the nut sedge was so pervasive that planting grass wasn't going to work. To get rid of the nut sedge, I would have to use a soil steriizer and I would not be able to plant anything in the ground for a year.

I did not want to not have plants for a year, so I killed everything with round up going several rounds with it. tilled up the soil to bring more of the nuts to the surface and repeated with more tilling and hand removal of any nuts that came up until no more nuts were coming up. I actually had to use a different weed killer that did a better job on nut sedge. I amended the soil and watered again to make sure no more weeds would come up. Then I bought sod and sodded the area. It was expensive and it was a small lawn. I had Emerald zoysia before, but I had to change to a different king of grass dwarf St Augustine because the shade from the city's tree was too dense for the zoysia and dwarf St Augustine was more shade tolerant. The blades of St. Augustine also looked more like the nut sedge so it could compete and hide the weeds better. The down side is that zoysia is a very thick grass that can squeeze out most weeds even most of the nut sedge, but it grows very slowly so it takes a long time to cover, it forms lumps that have to be cut off, and it not nice to walk on as it has a stiff grass blade, but it grows one inch a month so I only had to mow it once every couple of months with a power reel mower. Since this area was on the public side of my fence, I really did not want anyone on the grass.
St. Augustine has long runners that climb my fence and invade my border beds. It needs to be mowed more than I like. The HOA requires 50% grass in the 'front' yard, otherwise, I would not have grass at all, and just widen my borders and just have a paver path.

nut sedge is killed with sedge hammer and it only targets the nut sedge you can plant any time the guy that told you a year was a bum purslane is a succulent that's why it held water, seed in the fall and fertilize and water. in spring spray weed killer made for the lawn not round-up. the purslane should die feed and water your lawn or don't bother doing anything

I used image and sedge hammer both, but it takes a lot to kill the nutsedge and it isn't safe for all grasses.